The invention relates generally to imaging systems, and more particularly to high voltage generators for imaging systems.
Computed Tomography (CT) is an X-ray medical imaging process which makes possible obtaining a three-dimensional (3D) image of a patient or object using a plurality of two-dimensional (2D) images acquired about the patient or object. In CT, dual energy imaging is known for obtaining material characterizations and/or reduction of artifacts by utilizing two scans of the patient or object at different voltage/energy levels, “low-kV” and “high-kV.”
In a single rotation around the patient or object, a high voltage generator switches between “low-kV” and “high-kV” in order to emit low energy X-rays and high energy X-rays, respectively, from an X-ray tube. The high voltage generator may typically switch, for example, between a low-kV of about 70 to 100 kilovolts (kV) and a high-kV of about 120 to 150 kV. The low energy and high energy X-rays emitted, after being attenuated by the patient or object, impinge upon an array of radiation detectors. The intensity of the X-rays may then be processed to produce an image.
To complete a dual energy scan in a single rotation, the high voltage generator must rapidly switch between low-kV and high-kV. Such rapid switching may typically be performed periodically at a view rate frequency range of 1 kHz to 10 kHz. However, the high voltage generator typically includes a high voltage (HV) capacitance which may include a filtering capacitor and/or parasitic capacitance (such as from high voltage cabling). As a result, the fall time between high-kV and low-kV is related to the discharge of the HV capacitance.
In CT imaging, variations of kV waveforms from one view to another may cause undesirable image quality artifacts. What is needed is an improved technique for producing kV waveforms such that variations from one view to another are minimized.